1. Technical Field
This invention relates generally to invitro diagnostics, and more particularly to disposable invitro diagnostic cartridges and methods of performing invitro diagnostic tests.
2. Related Art
Diagnostic tests are increasingly being used to determine the state or condition of a biological environment, such as in human healthcare, agriculture, live stock management, municipal systems management, and national defense, by way of example and without limitation. A new market is emerging wherein diagnostic tests are being performed at the point-of-care. The diagnostic test can be complex, requiring multiple fluids and multiple steps to execute an assay. An assay is a sequence of steps or procedures used measure the presence or absence of a substance in a sample, the amount of a substance in a sample, or the characteristics of a sample. An example of a common and relative simple point-of-care assay, which can be readily conducted by a layperson, is a blood glucose test. In this test, generally speaking, the blood is mixed with glucose oxidase, which reacts with the glucose in the sample, creating gluconic acid, wherein the gluconic acid reacts with a chemical, typically ferricyanide, producing ferrocyanide. Current is passed through the ferrocyanide and the impedance reflects the amount of glucose present.
Although the aforementioned blood glucose assay is relative common and simple, many assays are far more complex, in that they require specific fluids, often of differing types and quantities, to be stored for future use on the diagnostic device. These fluids may be, but are not limited to, a buffer solution for dilution, fluids containing antibodies and antigens, microspheres coated with binding agents, cell lysing agents, and other fluids required to manipulate the sample being tested. Diagnostic tests that utilize millifluidic and microfluidic volumes of the fluids are intended to provide an incredibly high degree of specificity, sensitivity, and a precise volume and rate of fluid delivery to achieve as accurate a test result as possible. Nearly all microfluidic tests require the introduction of fluids throughout the assay sequence to manipulate the sample being tested and to produce an accurate diagnosis.
Typically, consumable diagnostic devices, meaning the diagnostic device is disposable upon being used, require a companion durable hardware device that interfaces with the consumable diagnostic device to execute the test. The durable hardware performs many functions, one of which is to facilitate dispensing a reagent in a reservoir or reagents from separate reservoirs on the consumable diagnostic into a specimen containing reaction chamber via microfluidic or millifluidic channels formed within the consumable diagnostic device. The introduction of the reagent into the reaction chamber requires precision; including flow rate, volume and timing, so as to best replicate the protocols of a laboratory where precession pipettes are employed. Upon the reagent being introduced into the reaction chamber, the reagent and specimen are generally kept in the reaction chamber for a minimum specified amount of time to allow the sample to mix as best possible with the reagent. Further, it is known to incorporate a mixing apparatus within the reaction chamber to further mix the specimen and the reagent prior to performing the analysis. The incorporation of a mixing member within the reaction chamber adds complexity, which can lead to error in test results, and further adds cost to the construction of the diagnostic device. Further yet, the mixing member can result in the specimen being over diluted, thereby resulting in volumetric loss of the specimen, and thus, resulting in a less than optimal, or failed test result.